Electric circuit interrupter



S. R. SMITH, JR

ELECTRIC CIRCUIT INTERRUPTER Jan. 4, 1949.

Filed April 23, 1943 3 mm M; w N\\ M n w V 0 i? h w M H :l M 2 F Y n m w a 12 Z a a, a I w a M a a I n M aw W Q .mw i] s H Patented Jan. 4, 1949 ELECTRIC CIRCUIT INTERRUPTER Sidney R. Smith, Jr., Pittsfield, Mass, assignor to General Electric Company, a corporation of New York Application April 23, 1943, Serial No. 484,232

Claims.

My invention relates to electric circuit interrupters, and more particularly to an electric fuse of the expulsion type.

When an electric circuit is opened by a circuit interrupter, the arc that is formed should be promptly extinguished. Various methods and means have been proposed for effecting are extinction. In expulsion fuses, for example, material is provided along the are path which Will evolve an arc-extinguishing medium due to the heat of the are that will assist in one Way or the other in effecting its extinction. Usually the material supplied for arc-extinguishing purposes exists in the form of a solid from which a vapor or a gas is evolved. In some cases, however, the arc-extinguishing material is initially in the form 'of a gas or a liquid. In many of the prior art arrangements, the effectiveness of the arcextinguishing material varied considerably with changes in the weather conditions. It is an object of my invention to provide a new and improved circuit-interrupting device in which the arc-extinguishing or arc-cooling means is unaffected by changes in weather conditions and which will not deteriorate merely with time in any way.

It is another object of my invention to provide arc-cooling means for a fuse of the expulsion type which is compact and inexpensive and which expels a large amount of arc-cooling vapor during the circuit-interrupting operation.

Still another object of my invention is to pro- 'vide new and improved arc-cooling means which is adapted for use with standard fuse links used in expulsion fuses.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this application.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. l is a sectional view of a portion of the fuseholder for an expulsion fuse including a fuse link embodying my invention; Fig. 2 illustrates my invention as applied to the cartridge type of expulsion fuse, while Fig. 3 is a View partly in section of an open type cutout embodying my invention.

From the following description it will become apparent that my invention is applicable to many different forms of fuses and particularly of the expulsion type. Although only several applications have been illustrated, it should be understood that these represent only a small number of the types of fuses to which my invention is applicable.

Referring now to Fig. 1 of the drawing, I have illustrated a portion of the fuse holder for an expulsion fuse generally indicated at if]. It should be understood that this fuse holder is adapted for use in fuse cutouts of the open or closed type such as are illustrated for example, in United States Letters Patents 1,973,265, Olsen et al., and 2,081,813, Hermann, both assigned to the same assignee as the present application. Fuse holder in comprises an insulating expulsion tube ll of pressed fiber or other suitable insulating material which does not carbonize, when subjected to the heat of an are which is extinguished in a relatively short time. An upper metal ferrule or contact terminal [2 is provided which is threadedly mounted to the upper end of tube II. A closure cap l3 threaded to ferrule l2 closes the upper end of tube H. Fuse holder I0 is adapted to be utilized in fuse cutouts of the type mentioned in the above-mentioned patents as well also as in other forms of fuse cutouts.

Since it is common practice to use universal cable type fuse links with a fuse holder H] such as is illustrated in Fig. 1, I have illustrated my invention as applied to such a fuse link, generally indicated at [4 in the drawing, which comprises a first or upper buttonhead terminal l5 which is adapted tobe clamped between the ferrule l2 and the cap l3 as indicated in Fig. 1. If desired, a suitable washer member 16 may be provided between buttonhead l5 and ferrule 12. The buttonhead terminal I5 is constructed so that when it is clamped between ferrule l2 and cap I3, the upper end of the fuse tube I l is completely sealed against the escape of gases.

The fuse link M is also provided with a second or lower terminal which comprises a flexible cable portion ll adapted to be connected to the lower contact terminal (not shown) of fuse holder l0. Electrically interconnecting these first and second fuse link terminals is a fusible element [8. This fusible element is preferably soldered as at I 9 to the lower fuse link terminal which includes a flexible cable portion IT. The upper end of fusible element I8 is soldered as at to upper buttonhead terminal l5. For certain current ratings it may be desirable to provide a strain wire such as 2| connected in parallel with fusible element |8 to prevent mechanical stresses from damaging fusible element l8 which is generally of softer metal having a low mechanical strength, especially when heated by carrying load currents. Preferably an insulating housing of tubular form such as 22 is provided to surround at least the lower portion of fusible element I8. Insulating housing 22 is preferably supported on fuse link l4 and upon rupture of fusible element |8 is blown out of fuse tube II with the lower fuse link portions.

In order greatly to increase the interrupting ability of the fuse link [4, I provide an hermetically sealed thin walled casing or container 23 which is formed by closing the ends of two concentric cylinders thereby providing a concentric passageway 24 through the container. The passageway 24 is of such a size as to fit closely about insulating tube 22 and the container 23 may or may not be arranged so as to be an integral part of fuse link l4. In Fig. 1, I have illustrated container 23 as being an integral part of fuse link l4 and is suitably fastened to buttonhead terminal it: as by solder indicated at 25. Container 23 may be formed of metal or if desired it may be molded from a suitable plastic material. Any suitable vaporizable arc-extinguishing liquid may be provided in hermetically sealed container 23 as indicated at 26, such for example, as water, carbon tetrachloride, a mixture of water and ethylene glycol, or a chlorinated aromatic hydrocarbon, such as is disclosed and claimed in United States Letters Patent 1,931,455, Clark. granted October 17, 1933, and assigned to the same assignee as the present application. Preferably the container 23 is not completely filled with the liquid 26 so that an unfilled portion 27 of container 23 is provided which acts as a cushioning means for the pressure rise occasioned by the high rate of evaporation of the liquid 26 during the arc interruption period. Also the unfilled portion 21 allows the liquid to expand and contract due to normal temperature variations without causing undue mechanical stresses on the container 23.

When the fusible element l8 ruptures, an arc is formed which arc, being in close contact with the hermetically sealed thin walled container 23 burns through the Walls of the container surrounding passageway 24 so as to vaporize the liquid 26 which can only escape through the bore of insulating tube 22 and expulsion tube I I. The are is therefore confined in a narrow passage along with a very high velocity vapor stream over its surface with the result that the arc is extinguished very rapidly. With this arrangement a very small amount of liquid is required which is used very efliciently in the tube II to interrupt high current arcs. It is also readily apparent that the arrangement described may be manufactured in a simple manner and fuse links embodying the invention may be used in standard forms of cutouts to replace fuse links which have a less satisfactory circuit-interrupting ability. It is further apparent that with this arrangement, substantially all of the liquid is usable quickly for arc-cooling purposes and since it is maintained in an hermetically sealed container, it will not deteriorate nor will changes in Weather conditions have any effect thereon.

edly mounted on an insulating member 5|,

In Fig. 2, I have illustrated my invention as applied to a cartridge type fuse having a tubular housing 30 of insulating material to which are threadedly mounted an upper fuse terminal 3| and a lower fuse terminal 32. Threadedly supported from upper fuse terminal 3| and within tubular casing 30 is a short fuse tube 33 having a relatively small bore. Preferably tube 33 is formed of an insulating material which is adapted to emit gas when subjected to the heat of an electric arc, although it might be constructed from any insulating material which does not readily carbonize. An hermetically sealed container 34 substantially identical with the container 23 of Fig. 1 is suitably mounted on the upper end of fuse tube 33, so that the cylindrical passageway 35 therethrough is in axial alignment with the bore 36 of short fuse tube 33. A suitable fuse link 31 of the buttonhead type is adapted to interconnect upper and lower fuse terminals 3| and 32. This fuse link 3'! is illustrated as comprising an upper buttonhead terminal 38 and a lower terminal comprising a flexible cable portion 39 which are interconnected by a fusible element 40. If desired a suitable strain wire M may also be provided in parallel with fusible element 40. The flexible cable portion 39 of fuse link 31 is electrically connected to lower fuse terminal 32 by any suit.- able means as indicated at 42,. The upper buttonhead terminal 38 on the other hand, is adapted to be supported by a suitable member 43 threadedly mounted in upper fuse terminal 3|. A suitable clamping member 44 threadedly engaging member 43, clamps the buttonhead terminal 38 against member 43 so that the upper end of casing 30 is sealed against the escape DI gases therefrom. If desired, fuse link 31 may be provided with a short insulating tube 45 enclosing at least a portion of fusible element). As in Fig. 1 hermetically sealed casing 34 is partially filled with a suitable arc-cooling liquid 46 which is vaporized when subjected to the heat of the arc, and a space ll for cushioning purposes is left at the upper end of hermetically sealed casing 34, which is only partially filled with the liquid 46.

The operation of the fuse disclosed in Fig. 2 will be obvious in view of the detailed descrip tion included above. Upon rupture of the fusible element 40 the are formed will burn through the Walls of hermetically sealed casing 34 .to vapor. ize the liquid 46 thereby producing a high velocity vapor stream over the entire surface of the are which is confined with the cooling stream in the small bore of fuse tube 33.

In Fig. 3, I have disclosed my invention as applied to .an open type fuse cutout. In Fig. 3 the member 3| is substantially the same as the upper fuse terminal 3| of Fig. 2 except that it is provided with an operating eye 50. The corresponding parts of Fig. 3 are designated by the same reference numerals as in Fig. 2. The member 3| and short fuse tube 33 are thread- In sulating member 5| is supported on an insulating support 52 which, in turn, is mounted on a hinge member 53. The flexible cable portion 39 of fuse link 31 is electrically connected to hinge member .53 as by clamping means 54. The support 52 is provided to give the electrical clear.- ance between upper contact 55 and lower eon tact 56 which may be mounted on any suitable support such as 5 7. Support 52 furthermore provides series insulation to keep the circuit Open once it has been opened, even though the interrupter comprising th fuse became currentconducting after interruption of the circuit. Lower contact 53 is provided with a hinge pin till which is engaged by a slot 53 in hinge member 53. A flexible lead 8i interconnects hinge member 53 and lower contact 5% to insure good electrical connection therebetween. Upper contact 555 on the other hand comprises ll-shaped spring contact member for electrically engaging member 35. Upper and lower contacts and 56 will be suitably connected to an associated electric circuit. When the cutout of Fig. 3 is operated as by means of a switch stick (not shown) engaging eye 5t, the cutout functions a, disconnecting switch. Under overload conditions the fuse linke 3? is ruptured and the dangling portion thereof will clearly indicate to a lineman that the fuse link should be replaced. in arrangements such as Figs. 2 and 3, it is also necessary to replace the hermetically sealed casing 3 5 whereas in the arrangement disclosed in Fig. 1 it is merely necessary to replace the fuse link which includes the hermetically sealed casing. It should be understood that the sealed casing of Fig. 1 could be replaceable while the casings of Figs. 2 and 3 might be integral with the fuse or fuse link.

From the above description it will be obvious that I have provided a new and improved arccooling means for circuit-interrupting devices such as fuses or other circuit-breaking devices of the expulsion type which will greatly increase the interrupting capacity, which will not deteriorate with time, or vary in effectiveness with weather conditions, which is simple to manufacture, and which is economical.

While I have illustrated specific embodiments of my invention, it should be understood that my invention is not limited to the specific details of construction and arrangement thereof herein illustrated and that changes and modifications may occur to one skilled in the art without departing from the spirit and scope of my invention. I aim in the appended claims to cover all such changes and modifications.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fuse link comprising a buttonhead terminal, a second terminal including a flexible cable portion, a fusible element electrically interconnecting said terminals, and adapted upon rupture thereof to produce an arc between said terminals, means for rapidly extinguishing said arc comprising an hermetically sealed thin walled metal container supported as an integral part of said fuse link and having an arc passageway therethrough positioned so that said are will extend into said passageway, and a vaporizable liquid in said container, said container electrically connected to one of said terminals and said passageway normally being free of said liquid, said are upon operation of said fuse link burning through the walls of said container to vaporize said liquid and cause rapid extinguishment of said arc.

2. A circuit-interrupting device comprising a tubular insulating casing, a pair of terminals one mounted at either end of said casing, a fusible element electrically interconnecting said terminals, and adapted upon rupture thereof to produce an are between said terminals, means associated with said circuit-interrupting device for rapidly extinguishing said are comprising an hermetically sealed thin Walled cylindrical metal container having a concentric arc passageway therethrough positioned with respect to said fusible element so that said are will extend into said passageway, and a vaporizable liquid in said container, contc er electrically connected to one of said tern is and said passageway normally being free or" said liquid, said arc upon operation of circa J interrupting device burr ng through the walls of said container to i said lipid and cause rapid extinguish ment of said arc.

3. In a circ ting device, a pair of terminals, a fi lble ele interconnecting said terminals ed up n rupture thereof to produce b' said terminals and an hermetically seal d thin walled metal casing electrically to one or" said terminals and containing an arc extinguishin material, said casing being provided with an arc passageway therethrough and positioned so that said are extends into sa d passageway upon operation of said circuit int upting device whereupon the wall of said casing is burned through and said material is released to aid in extinguishing said arc.

4. In a circuit interrupting device, a pair of terminals, a fusible element interconnecting said :inals and adapted upon rupture thereof to produce an are between said terminals, and an hermetically sealed thin wall metal casing electrically connected to one of said terminals and containing arc extinguishing liquid, said casing being provided with an arc passageway there'through normally free of said liquid and being positioned so that said are is produced in said passageway upon operation of said circuit interrupting device and burns through the walls of said casing to vaporize said liquid which aids in extinguishing said arc.

5. A circuit interrupting device comprising a tubular insulating casing, a pair of terminals mounted respectively at opposite ends of said casing, a fusible element interconnecting said terminals and adapted upon rupture thereof to produce an are between said terminals, means for rapidly extinguishing said arc comprising an hermetically sealed thin walled metal container electrically connected to one of said terminals and having a vaporizable liquid therein, said container having an arc passageway therethrough and so associated with said device that upon rupture of said fusible element said are will extend into said passagawey whereby the wall of said container is burned through and said liquid is vaporized and released to cause rapid extinguishment of said are.

SIDNEY R. SMITH, JR.

EF'ERENCES CITED 

